Jake Peavy was brought in to help San Francisco reach the postseason, and his first start for the Giants could return them to first place in the NL West.
A day after coming over in a trade, Peavy will try to help the Giants halt their three-game slide and overtake the division-leading Dodgers on Sunday night (8:07 p.m.).
With Matt Cain's return from right elbow inflammation unclear, San Francisco (57-47) acquired Peavy from Boston in exchange for two minor league pitchers on Saturday to help fortify a rotation that owns a 3.67 ERA.
"The impetus to execute the trade was accelerated by the news we got about Matt Cain becoming more and more tenuous," general manager Brian Sabean said.
The move reunites Peavy - a World Series champion with the Red Sox last year - with manager Bruce Bochy after they spent 2002-06 together in San Diego (see full preview).
Athletics at Rangers, 7:05 p.m.
The Oakland Athletics rebounded from a rare poor pitching performance by giving the ball to one of their 11-game winners and finding their power stroke offensively.
Now the A's are turning to their other 11-win pitcher as they go for the series win in Arlington.
Scott Kazmir looks to extend his outstanding stretch on the mound Sunday night when he tries to lead MLB-best Oakland to its eighth victory in nine road meetings with the baseball-worst Texas Rangers.
Oakland starters have the AL's lowest ERA at 3.14, including a MLB-best 2.21 mark since July 3. The A's, however, suffered a 4-1 loss in Friday's opener when struggling Jason Hammel allowed four runs over 5 2-3 innings (see full preview).
Padres at Braves, 5:05 p.m.
Atlanta's slumbering offense woke up to get the Braves back in the win column, and it may have happened just in time considering Mike Minor's recent struggles.
The left-hander seeks his first home victory in over two months Sunday night when the Braves look to notch back-to-back wins in a four-game set against the San Diego Padres.
Atlanta (56-48) hit .196 during a 1-4 stretch to fall 2 1/2 games behind NL East-leading Washington before Freddie Freeman and Tommy La Stella led an 11-hit attack with three apiece in Saturday's 5-3 win.
Chris Johnson also drove in a pair of runs to help the Braves move within 1 1/2 of the Nationals, who lost at Cincinnati (see full preview).